Serguei,
> On 17/04/2020, at 2:24 AM, Sokol Serguei <so...@insa-toulouse.fr> wrote:
>
> Hi,
>
> I would like to make a suggestion for a small syntactic modification of FUN
> argument in the family of functions [lsv]apply(). The idea is to allow
> one-liner expressions without typing "function(item) {...}" to surround them.
> The argument to the anonymous function is simply referred as ".". Let take an
> example. With this new feature, the following call
>
> sapply(split(mtcars, mtcars$cyl), function(d) summary(lm(mpg ~ wt,
> d))$r.squared)
> # 4 6 8
> #0.5086326 0.4645102 0.4229655
>
>
> could be rewritten as
>
> sapply(split(mtcars, mtcars$cyl), summary(lm(mpg ~ wt, .))$r.squared)
>
> "Not a big saving in typing" you can say but multiplied by the number of
> [lsv]apply usage and a neater look, I think, the idea merits to be considered.
It's not in any way "neater", not only is it less readable, it's just plain
wrong. What if the expression returned a function? How do you know that you
don't want to apply the result of the call? For the same reason the
implementation below won't work - very often you just pass a symbol that
evaluates to a function and always en expression that returns a function and
there is no way to distinguish that from your new proposed syntax. When you
feel compelled to use substitute() you should hear alarm bells that something
is wrong ;).
You can certainly write a new function that uses a different syntax (and I'm
sure someone has already done that in the package space), but what you propose
is incompatible with *apply in R (and very much not R syntax).
Cheers,
Simon
> To illustrate a possible implementation, I propose a wrapper example for
> sapply():
>
> wsapply=function(l, fun, ...) {
> s=substitute(fun)
> if (is.name(s) || is.call(s) && s[[1]]==as.name("function")) {
> sapply(l, fun, ...) # legacy call
> } else {
> sapply(l, function(d) eval(s, list(.=d)), ...)
> }
> }
>
> Now, we can do:
>
> wsapply(split(mtcars, mtcars$cyl), summary(lm(mpg ~ wt, .))$r.squared)
>
> or, traditional way:
>
> wsapply(split(mtcars, mtcars$cyl), function(d) summary(lm(mpg ~ wt,
> d))$r.squared)
>
> the both work.
>
> How do you feel about that?
>
> Best,
> Serguei.
>
> ______________________________________________
> R-devel@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>
______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
